The invention relates to a hydraulically actuatable safety valve and in particular to a safety valve with a valve housing accommodating two valve bodies movable in opposite direction toward each other in a bore of the housing, two e.g. electromagnetically actuatable pilot valves, an inlet port for connection to a pump, a working port and an outlet port for connection to a tank, with each valve body including a working piston acted upon by a pressure fluid via the pilot valves and control channels, and further including at least one control piston connected to the working piston and regulating the passageways between the working port, the pump port and the tank port wherein the working port is connectable to the tank port upon occurrence of a faulty switching.
A safety valve of this kind is known from German patent No. 31 04 957 and is used, for example, for controlling the brake and the clutch of a mechanical press. This known safety valve includes two directional control valves which ensure a braking action upon failure of one valve. The directional control valves are checked automatically without requiring any additional devices such as, for example, electric checking elements.